A compact electrochemical sensor such as a glucose sensor includes a reference electrode in addition to a working electrode and a counter electrode in many cases. In such an electrochemical sensor, a silver/silver chloride electrode (Ag/AgCl electrode) is generally used as the reference electrode.
[Patent document 1] Japanese Patent No. 3104672
A silver/silver chloride electrode of an electrochemical sensor is formed, for example, on an underlying electrode provided on a base member of the electrochemical sensor. Each of electrodes (a working electrode, a counter electrode and the underlying electrode) of a recent electrochemical sensor has a very small size. Besides, a distance between the electrodes is also small, and therefore, it is difficult to form, in a recent electrochemical sensor, a silver/silver chloride electrode so as not to cause a short circuit. Furthermore, when measurement is performed with the electrochemical sensor for a long period of time, there arises a problem in which the potential of the reference electrode is not stable due to elution of silver/silver chloride.
Accordingly, an object of an embodiment of the present invention is to provide a technique in which a margin regarding the range or the position of forming a silver/silver chloride electrode may be increased, and in which elution of silver/silver chloride is suppressed to stabilize the potential of the silver/silver chloride electrode (reference electrode).